To investigate the role of dopamine transporters in the pathophysiology of cocaine dependence complicated by Attention Deficit-Hyperactivity Disorder (ADHD). To date, 6 patients with cocaine dependence and ADHD, 11 patients with cocaine dependence without ADHD and 8 healthy nonaddicted subjects have been studied. Preliminary data do not suggest that dopamine transporter availability is different in cocaine dependent patients with ADHD relative to cocaine dependent patients without ADHD.